Anaplasmosis, a vector-borne rickettsial disease of cattle, sheep and goats is caused by three species; Anaplasma marginale, Anaplasma centrale and Anaplasma ovis. Clinical disease is characterized by anemia, weight loss, abortion and death. Survivors are lifelong carriers of the rickettsia. Eventual control of Anaplasma species infection will require both an effective vaccine and identification of carrier cattle, sheep or goats. Two possible methods for routine carrier identification are a nucleic acid probe for hybridization of infected blood or the detection of Anaplasma species-specific antibody is serum. Hybridization of DNA extracted from blood with an Anaplasma marginale-specific nucleic acid probe does not always detect known carriers, because of cyclic changes in rickettsemia levels. Carrier identification by antibody requires that infected animals never clear the rickettsia. Indefinite persistence of Anaplasma marginale in infected cattle has been documented. Current serological tests for anaplasmosis are not widely used, primarily because the error rate is high. One problem with current tests is false positive results caused by erythrocyte contamination of the Anaplasma marginale antigen used in the tests, and the presence of anti-erythrocyte antibody in the sera of some cattle.
Recently, progress has been made toward the characterization of a surface membrane protein of Anaplasma marginale for use in diagnosis (N. Tebele, T. C. McGuire, and G. H. Palmer, Infect. Immun. 59:3199-3204, 1991 and E. S. Visser, T. C. McGuire, G. H. Palmer, W. C. Davis, V. Shkap, E. Pipano, and D. P. Knowles, Jr., Infect. Immun. 60:5139-5144, 1992.). This protein, designated major surface protein 5 (MSP-5) and monoclonal antibody ANAF16C1 were shown to have utility when used together in the competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) format (Anderson, J. Immunol. Meth., 74:139-149, 1984) for the diagnosis of cattle, sheep and goats infected with Anaplasma marginale, Anaplasma centrale and Anaplasma ovis (E. S. Visser, T. C. McGuire, G. H. Palmer, W. C. Davis, V. Shkap, E. Pipano, and D. P. Knowles, Jr., Infect. Immun. 60:5139-5144, 1992.).